Damp Basement

HI There!

So I am a first time home buyer and the house I bought has a very damp/humid basement in Virginia. It doesn't look like I have any water problems or leaks, which I guess is good. I bought a dehumidifier, (home depot type) a few months ago and it runs non-stop to keep the humidity around 55-60%. If I turn it off it goes up to about 80-85%. I've read over some of the topics you guys have covered before and I do have gutters which are directing the water away from the house. The ground slopes away from the house, but the soil is clay. I'm wondering what my next step should be. Should I put in a larger whole house style dehumidifier or are there other steps I can take to help reduce the dampness in the basement. I want to get this resolved before I start putting furniture and such down there. Any thoughts or help would be appreciated!